This module is meant to be the definitive implementation of iterators,
as popularized by Mark Jason Dominus's lectures and recent book (_Higher
Order Perl_, Morgan Kauffman, 2005).

An "iterator" is an object, represented as a code block that generates
the "next value" of a sequence, and generally implemented as a closure.
Iterator.pm provides a class that simplifies creation and use of these
iterator objects.
